A conventional compressor, as shown in FIG. 10, has an upper frame 100 of a cylinder having a discharge hole 100a opening within the cylinder, a discharge valve 101 for opening and closing the discharge hole 100a of the upper frame 100, a valve holding member 102 for sandwiching the discharge valve 101 in cooperation with the upper frame 100, and a fixing bolt 103.
The valve holding member 102 has a through hole 102a, and the upper frame 100 has a screw hole 100b. 
Then, the fixing bolt 103 is inserted into the through hole 102a of the valve holding member 102 and is screwed with the screw hole 100b of the upper frame 100. As a result, the discharge valve 101 is sandwiched and held between the upper frame 100 and the valve holding member 102 (see JP 61-5373 U).
However, with the conventional compressor as shown above, in which the upper frame 100 has the screw hole 100b, there has been a need for increasing the thickness of the upper frame 100 to ensure an effective thread length. This would result in increased axial (thicknesswise) sizes of the screw hole 100b of the upper frame 100, which in turn would result in increased capacities (hereinafter, referred to as top clearance) of the discharge hole 100a of the upper frame 100.
Thus, such a large top clearance would lead to an increased quantity of compressed gas remaining in the discharge hole 100a at an end of compression, which would incur efficiency degradation of the compressor as well as increase of operating noise due to re-expansion of the compressed gas derived from within the discharge hole 100a. 
More specifically, the capacity efficiency would lower with a low-speed operation of the compressor, while the motive power would increase with a high-speed operation of the compressor. Besides, a pulsating pressure caused by the re-expansion of compressed gas would incur increase of the operating noise.